Dendritic Cell Vaccines Against Her2/Her3 and Pembrolizumab for the Treatment of Brain Metastasis From Triple Negative Breast Cancer or HER2+ Breast Cancer

This study is testing a personalized vaccine combined with an immunotherapy drug (pembrolizumab) for women with breast cancer that has spread to the brain. The vaccine is made from the patient's own immune cells (dendritic cells) and is designed to train the immune system to recognize and attack cancer cells that carry HER2 or HER3 proteins. **You may be eligible if:** - You are a woman with breast cancer — either triple-negative breast cancer or HER2-positive breast cancer — that has spread to the brain - You are not pregnant, not breastfeeding, and willing to use effective birth control throughout the study (which may be several years) - You meet additional health requirements your doctor will review **You may NOT be eligible if:** - You are pregnant or breastfeeding - You are unwilling to use contraception during the study period - You do not meet specific health and disease criteria your doctor will assess Talk to your doctor to see if this trial is right for you.